1. Field of the Invention
The present invention relates to an electronic timepiece and a control method of an electronic timepiece.
2. Background Art
An analog electronic timepiece is known which displays the time on a dial by using an indicating hand. Some analog electronic timepieces have a timer function or as stopwatch function. In these electronic timepieces, a fast-forwarding operation of the indicating hand is performed, when the time is corrected, or when the indicating hand is returned to an initial position in order to use the timer function or the stopwatch function. In the analog timepieces, the indicating hand is driven in a normal direction and in a reverse direction thereof by a stepping motor. The normal direction represents a clockwise rotating direction. The indicating hand includes an hour hand which rotates once in 12 hours, a minute hand which rotates once in 60 minutes, a second hand which rotates once in one minute, and a functional hand used for the timer function or the stopwatch function. The stepping motor performs a rotary operation using a drive pulse having a pulse width corresponding to a predetermined drive voltage and a predetermined drive frequency, and drives each indicating hand via a train wheel mechanism.
For example, in an analog electronic timepiece disclosed in JP-A-2-138895, a voltage stabilizer circuit generates a low constant voltage of approximately 1.2 V from a battery voltage (approximately 1.58 V). Then, the analog electronic timepiece disclosed in JP-A-2-138895 uses the generated low constant voltage so as to perform driving for forwarding the indicating hand at normal speed on a time display and driving for forwarding a position of the functional hand at fast speed in the stopwatch function. In a case of the time display, driving the hour hand, the minute hand, and the second hand at normal speed is referred to as a normal hand operation, and driving the indicating hand at fast-forwarding speed is referred to as a fast-forwarding hand operation.
In recent years, an analog electronic timepiece is known in which light energy is converted into electrical energy by using a solar cell and the converted electrical energy is stored in a secondary battery so as to be used for power to drive the indicating hand. For example, a voltage value of the secondary battery is 2.0 V to 2.6 V. Therefore, this analog electronic timepiece uses a voltage of the secondary battery by causing a regulator to convert the voltage into a constant voltage of 2.2 V, for example.
For example, in an analog electronic timepiece disclosed in JP-A-2012-145594, a voltage value of a secondary battery which stores electrical energy generated by a generating device is detected. Then, when the detected voltage value is equal to or greater than a predetermined value, a control logic circuit performs discharge control by performing control for causing a discharge current to flow to a drive circuit. In this manner, the analog electronic timepiece disclosed in JP-A-2012-145594 utilizes a constant voltage which is rapidly lowered from a voltage to be supplied to a motor. The reason for the discharge is to prevent a step-out phenomenon. The step-out phenomenon means a phenomenon in which a stepping motor cannot be stopped at a predetermined position since energy of an input pulse deviates from a target.